Additives for improving the resistance to wear and lacquering of vehicle fuels of the gas oil or bio gas oil type

ABSTRACT

The present disclosure relates to anti-lacquering additives for vehicle fuels of the gas oil or bio gas oil type having a sulphur content less than or equal to 500 ppm by mass. These additives also improve the lacquering resistance of the higher-grade vehicle fuels of gas oil or bio gas oil type having a sulphur content less than or equal to 500 ppm by mass.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Entry of International Application No. PCT/EP2013/067311, filed on Aug. 20, 2013, which claims priority to French Patent Application Serial No. 1257939, filed on Aug. 22, 2012, both of which are incorporated by reference herein.

BACKGROUND AND SUMMARY

A subject of the present invention is additives making it possible to limit the formation of soaps and/or varnishes in the internal parts of the injection systems of engines for (bio)gas oil type vehicle fuels, i.e. in particular to increase their resistance to lacquering.

Gas oil or diesel is a vehicle fuel for diesel engines (compression engines) comprising middle distillates with a boiling point comprised between 100 and 500° C. A gas oil can be constituted by a mixture of middle distillates of fossil origin and biofuels. By biofuel, is meant the vehicle fuels obtained from organic matter (biomass), as opposed to the vehicle fuels originating from fossil resources. There can be mentioned, as examples of known biofuels, the bio gas oils (or also called biodiesel) and the alcohols.

Biodiesel or bio gas oil is an alternative to standard vehicle fuel for diesel engines. This biofuel is obtained from vegetable or animal oil (including used cooking oils) converted by a chemical process called transesterification causing this oil to react with an alcohol in order to obtain fatty acid esters. With methanol and ethanol, fatty acid methyl esters (FAMEs) and fatty acid ethyl esters (FAEEs) are obtained respectively.

Mixtures of middle distillates of fossil origin and bio gas oil are denoted by the letter “B” followed by a number indicating the percentage of bio gas oil contained in the gas oil. Thus, a B99 contains 99% bio gas oil and 1% middle distillates of fossil origin, and B20 contains 20% bio gas oil and 80% middle distillates of fossil origin etc.

Gas oil vehicle fuels of the B0 type, which do not contain oxygen-containing compounds are therefore distinguished from bio gas oil vehicle fuels of the Bx type which contain x % (v/v) vegetable oil esters or fatty acid esters, most often methyl esters (FAME or VOME). When the bio gas oil is used alone in the engines, the vehicle fuel is denoted by the term B100. In the remainder of the present application, the term (bio) gas oil is used to identify the B0 or Bx type vehicle fuels for diesel engines (compression engines).

In many countries the sulphur content of (bio) gas oil vehicle fuels has been subject to a very significant reduction for environmental reasons, in particular in order to reduce the SO₂ emissions. For example in Europe, the maximum sulphur content of road gas oil type vehicle fuels is currently 10 ppm by mass.

As well as reducing the sulphur content, the methods of preparation of low-sulphur gas oil or diesel vehicle fuel bases, for example hydrotreatment methods, also reduce the polycyclic aromatic compounds and polar compounds contained in these gas oil vehicle fuel bases for diesel engines. It is known that gas oil or diesel vehicle fuels having a low (less than 100 ppm) or even very low sulphur content have a reduced ability to lubricate the engine fuel injection system, which results for example in early failure of the engine fuel injection pump during the lifetime of the engine, failure occurring for example in high-pressure vehicle fuel injection systems, such as high-pressure rotary distributors, in-line pumps and combined pump-injector units. In order to compensate for the loss of compounds ensuring the lubricating character of these vehicle fuels, numerous lubricity and/or anti-wear and/or friction modifying additives have been introduced into the fuels on the market. Their characteristics are broadly described in the patents EP 915944, EP 839174 and EP680506.

It is known that the diesel vehicle fuels on the market must meet national or supranational specifications (for example standard EN 590 for diesel vehicle fuels in the EU). For commercial vehicle fuels, there is no legal obligation regarding the incorporation of so-called performance additives (chemical compounds incorporated in fuels to improve their properties, for example detergent additives, friction-reducing additives, anti-corrosion additives, anti-foaming additives and additives for improving low temperature performance); the oil companies and the distributors are free to add or not add additives to their vehicle fuels. From a commercial standpoint, in the field of distribution of fuels, a distinction is made between the “standard or entry-level” fuels, with little or no additives, and higher-grade fuels, in which one or more additives are incorporated to improve their performance (above the regulation performance). Within the meaning of the present invention, by higher-grade vehicle fuel of the gas oil or bio gas oil type is meant any gas oil or bio gas oil vehicle fuel to which at least 50 ppm by mass of deposit reducing and/or detergent and/or dispersant additives have been added.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph of a diesel engine injector with high-pressure direct injection;

FIG. 2 is a photograph of a needle of a diesel engine injector with direct injection, fouled with soap and/or varnish type deposits (“lacquering”);

FIG. 3 is a photograph of a nozzle of a diesel engine injector with indirect injection, fouled with coking type deposits; and

FIG. 4 is a photograph of a needle of a diesel engine injector with direct injection, fouled with soap and/or varnish type deposits (“lacquering”).

DETAILED DESCRIPTION

As shown in FIGS. 1 and 2, it has been found that during the use of certain higher-grade (bio) gas oil vehicle fuels, deposits 1 appear on the needles 2 of the injector 3 of the injection systems of diesel engines, in particular those of Euro 3 to Euro 6 type. Thus, the use of anti-wear and/or friction modifying and/or anti-coking type deposit additives have sometimes exhibited unsatisfactory, or even very unsatisfactory, resistance to lacquering. This results in the formation of deposit 1 generally covered by the term “lacquering”, which will be used hereinafter, or the acronym IDID (internal diesel injector deposits).

Within the meaning of the present invention, the lacquering phenomenon does not relate to the deposits which are present on the outside of the injection system 5 or 5′ (FIGS. 1 and 3) and which are associated with coking which gives rise to fouling and partial or total blocking of the injection nozzles 4 or 4′ (nozzle “coking” or “fouling”). Lacquering and coking are two phenomena clearly distinguished by:

-   -   the causes of these deposits,     -   the conditions for the appearance of these deposits and,     -   the site where these deposits are produced.         Coking is a phenomenon which appears only downstream of a diesel         injection system.

As shown in FIG. 3, the deposits 5′ formed are characterized in that they are constituted by pyrolysis of the hydrocarbons entering the combustion chamber and have the appearance of carbonaceous deposits. In the case of high-pressure direct injection diesel engines, it has been found that the coking tendency is much less marked. This coking is simulated in the CEC F098-08 DW10B standard engine test, in particular when the vehicle fuel tested is contaminated with metallic zinc.

In the case of indirect injection engines, the injection of the vehicle fuel is not carried out directly in the combustion chamber as in the case of direct injection engines. As described for example in U.S. Pat. No. 4,604,102, there is a prechamber before the combustion chamber into which the fuel is injected. The pressure and the temperature in a prechamber are below those of a combustion chamber of direct injection engines.

Under these conditions, the pyrolysis of the vehicle fuel produces carbonaceous particles which are deposited on the surface of the nozzles 4′ of the injectors (“throttling diesel nozzle”) and block the apertures 6 of the nozzles 4′ (FIG. 3). Only the surfaces of the nozzle 4′ exposed to the combustion gases are at risk of carbon deposits (coking). In terms of performance, the phenomenon of coking causes a loss of engine power.

Lacquering is a phenomenon that appears only in direct injection diesel engines and only occurs upstream of the combustion chamber, i.e. in the injection system. As shown in FIGS. 1 and 2, the injectors 3 of direct injection diesel engines comprise a needle 2 the lift of which allows precise control of the quantity of fuel injected at high pressure directly into the combustion chamber.

The lacquering causes the appearance of deposits 1 which appear specifically at the level of the needles 2 of the injectors 3 (FIGS. 1 and 2). The lacquering phenomenon is linked to the formation of soap and/or varnish in the internal parts of the injection systems of engines for (bio) gas oil type fuels. The lacquering deposit 1 can be located on the end 4 of the needles 2 of the injectors 3, both on the head and on the body of the needles 2 of the vehicle fuel injection system but also throughout the entire needle lift control system (valves not shown) of the injection system. This phenomenon is particularly marked in the case of engines using higher-grade (bio) gas oil vehicle fuels. When these deposits are present in large quantities, the mobility of the needle 2 of the injector 3 fouled with these deposits 1 is compromised. This lacquering phenomenon can eventually generate a loss of flow rate of vehicle fuel injected and therefore a loss of engine power.

Moreover, unlike coking, lacquering can also cause an increase in engine noise and sometimes starting problems. Indeed, the parts of the needles 2 fouled by the deposits of soap and/or varnish 1 can adhere to the internal walls of the injector 3. The needles 2 are then blocked and the fuel can no longer pass through.

Generally a distinction is made between 2 types of deposits of the lacquering type:

1. deposits that are rather whitish and powdery; on analysis, it is found that these deposits consist essentially of soaps of sodium (sodium carboxylates, for example) and/or calcium (type 1 deposits);

2. organic deposits resembling coloured varnishes localized on the needle body (type 2 deposits).

Regarding the type 1 deposits, there are many possible sources of sodium in bio gas oil vehicle fuels of the Bx type:

catalysts for transesterification of vegetable oils for producing esters of the fatty acid (m)ethyl ester type such as sodium formate;

another possible source of sodium can be from the corrosion inhibitors used when petroleum products are conveyed in certain pipes, such as sodium nitrite;

finally, accidental exogenous pollution, via water or air for example, can contribute to the introduction of sodium into vehicle fuels (sodium being a very widely occurring element).

There are many possible sources of acids in vehicle fuels of the Bx type, for example:

-   -   residual acids in biofuels (see standard EN14214 which fixes a         maximum permitted level of acids)     -   corrosion inhibitors used in the conveyance of petroleum         products in certain pipes such as DDSA (dodecenylsuccinic         anhydride) or HDSA (hexadecenylsuccinic anhydride) or some of         their functional derivatives such as acids.

With regard to type 2 organic deposits, some publications state that they may in particular result from reactions between deposit reducers/dispersants used to prevent coking (for example PIBSI type detergents which are derivatives of polyamines) and acids (which would be present inter alia as fatty acid ester impurities in bio gas oil). In the publication SAE 880493, Reduced Injection Needle Mobility Caused by Lacquer Deposits from Sunflower Oil, the authors M Ziejewski and H J Goettler describe the lacquering phenomenon and its harmful consequences for the operation of engines operating with sunflower oils as vehicle fuel. In the publication SAE 2008-01-0926, Investigation into the Formation and Prevention of Internal Diesel Injector Deposits, the authors J Ullmann, M Geduldig, H Stutzenberger (Robert Bosch GmbH) and R Caprotti, G Balfour (Infineum) also describe the reactions between acids and deposit reducers/dispersants to explain the type 2 deposits.

Moreover, in the publication SAE International, 2010-01-2242, Internal Injector Deposits in High-Pressure Common Rail Diesel Engines, the authors S. Schwab, J. Bennett, S. Dell, J. Galante-Fox, A. Kulinowski and Keith T. Miller explain that the internal parts of the injectors are generally covered with a slightly coloured deposit which is visible to the naked eye. Their analyses made it possible to determine that it mainly comprised sodium salts of alkenyl (hexadecenyl or dodecenyl) succinic acids; the sodium originating from dehydrating agents, from caustic solutions used in the refinery, from tank bottom water or from seawater, and the succinic diacids being used as corrosion inhibitors or present in multifunctional additive packages. Once formed, these salts are insoluble in low-sulphur diesel fuels, and as they are in the form of fine particles they pass through gas oil filters and are deposited inside the injectors. In this publication, the development of an engine test is described, making it possible to reproduce the deposits. This publication emphasizes that only the diacids generate deposits, in contrast to monocarboxylic acids or the neutral esters of organic acids.

In the publication SAE International, 2010-01-2250, Deposit Control in Modern Diesel Fuel Injection System, the authors, R. Caprotti, N. Bhatti and G. Balfour, also investigate the same type of internal deposits in the injectors and assert that the appearance of deposits is not linked specifically to one type of vehicle fuel (B0 or containing FAME(Bx)) nor to vehicles of one type (light vehicles or heavy goods vehicles) equipped with modern motorizations (common rail). They demonstrate the performance of a new deposit reducer/dispersant, effective on all types of deposits (coking and lacquering).

The present invention proposes additives with preventive and curative effects, making it possible to limit the soap and/or varnish deposits in the internal parts of the injection systems, i.e. to improve resistance to the phenomenon of lacquering in engines using higher-grade (bio) gas oil and/or (bio) diesel type vehicle fuels, the sulphur content of which is less than or equal to 500 ppm by mass, and which comprise at least 50 ppm by mass of deposit reducer(s) and/or detergents and/or dispersant(s). These additives therefore prevent these deposits to form (preventive), and allow when they are formed, to be removed by render the injectors cleaner (curative).

These problems of the resistance to lacquering of (bio) gas oil type vehicle fuels are solved by the use of at least one additive which comprises at least 50% by mass of partial polyol ester(s), said polyol esters comprising x ester units, y hydroxylated units and z ether units, x, y and z being integers such that x varies from 1 to 10, y varies from 1 to 10, and z varies from 0 to 6, preferably x varies from 1 to 10, y varies from 3 to 10, and z varies from 0 to 6. The synthesis of partial polyol esters is known per se; they can for example be prepared by esterification of fatty acid(s) and linear and/or branched polyols optionally comprising (hetero)cycles of 5 to 6 atoms bearing hydroxyl functions. The product(s) originating from this esterification reaction comprise(s) a distribution of ester units, hydroxylated units and ether units such that x varies from 1 to 4, y varies from 1 to 7 and z varies from 1 to 3. Generally this type of synthesis leads to a mixture of mono-, di-, tri- and optionally tetra-esters as well as small quantities of fatty acid(s) and polyols which have not reacted.

According to an embodiment, the polyol esters are obtained by esterification of fatty acid(s) and of linear and/or branched polyols optionally comprising heterocycles of 4 to 5 carbon atoms and an oxygen atom, bearing hydroxyl functions. Within the framework of the present invention, the polyols will be chosen from the linear polyols comprising more than three hydroxyl functions and the polyols comprising at least one (hetero)cycle of 5 or 6 atoms, preferably heterocycles of 4 to 5 carbon atoms and an oxygen atom, optionally substituted by hydroxyl groups, these polyols being able to be used alone or in a mixture. In the remainder of the present discussion, these polyols are referenced R in the formulations mentioned below.

Among the polyols R, the polyols with linear or branched hydrocarbon chains comprise at least four units represented in formula (I) below:

H—(OCH₂)_(p)—(CHOH)_(q)—(CH₂OH)  (I)

With p and q being integers, p being equal to or greater than 0, q is greater than 2, these numbers not being able to exceed 10.

Among the polyols R, the polyols with linear or branched hydrocarbon chains comprise at least four units represented in formula (II) below:

H—(OCH₂)_(p)—(CR1R2)_(q)-(CH₂OH)  (II)

With p and q being integers, p being equal to or greater than 0, q is greater than 1, these numbers not being able to exceed 5, R1 and R2 are identical or different and represent either the hydrogen atom, or a —CH₃ or —C₂H₅ group or a —CH₂—OH group.

Among the polyols R, some comprise at least one (hetero)cycle of 4 or 5 carbon atoms and an oxygen atom, optionally substituted by hydroxyl groups and correspond to general formula (III) below:

with s and t being integers, and when s is equal to 1, t is equal to 3 and when s is zero, t is equal to 4.

Among the polyols R, some comprise at least two heterocycles of 4 or 5 carbon atoms and one oxygen atom connected by the formation of an acetal bond between a hydroxyl function of each ring, those heterocycles being optionally substituted by hydroxyl groups. Preferably, the polyols are chosen from the group comprising erythritol, xylitol, D-arabitol, L-arabitol, ribitol, sorbitol, malitol, isomalitol, lactitol, sorbitan, volemitol, mannitol, pentaerythritol, 2-hydroxymethyl-1,3-propanediol, 1,1,1-tri(hydroxymethyl)ethane, trimethylolpropane and carbohydrates such as sucrose, fructose, maltose, glucose and saccharose, preferably sorbitan. According to a preferred variant, the partial polyol esters are chosen from the partial sorbitan esters, preferably sorbitan monooleate, used alone or in a mixture.

The fatty acids from which the esters according to the invention originate can be chosen from the fatty acids the chain length of which varies from 10 to 24 carbon atoms and/or at least one diacid substituted by at least one polymer, for example poly(iso)butene comprising from 8 to 100 carbon atoms. They are preferably chosen, in the case of the mono acids, from the stearic, isostearic, linolenic, oleic, linoleic, behenic, arachidonic, ricinoleic, palmitic, myristic, lauric and capric acids, and mixtures thereof and, in the case of the diacids from the alkyl- or alkenylsuccinic, alkyl- or alkenylmaleic acids. The fatty acids can originate from the transesterification or the saponification of vegetable oils and/or animal fats. The preferred vegetable oils and/or animal fats are chosen according to their oleic acid concentration. Reference may be made for example to Table 6.21 of Chapter 6 of the publication Carburants & Moteurs by J. C. Guibet and E. Faure, 2007 edition in which the compositions of several vegetable oils and animal fats are given. The fatty acids can also originate from tall oil fatty acids which comprise a majority of fatty acids, typically greater than or equal to 90% by mass as well as resin acids and unsaponifiables in a minority, i.e. in quantities generally less than 10%.

Preferred additives according to the invention capable of improving the lacquering resistance of higher-grade (bio)diesel vehicle fuels comprise partial sorbitan esters. Other preferred additives comprise at least 50% by mass of mono- and/or diester(s) of isobutylenesuccinic acid and polyols according to one of formulae I to III. Other preferred additives comprise at least 50% by mass of mono- and/or diester(s) of monocarboxylic acids with 12 to 24 carbon atoms and polyols according to one of formulae I to III.

The invention also relates to an additive package for (bio) gas oil vehicle fuels containing at least one lacquering resistance additive as defined previously and at least one or more other functional additives, such as deposit reducers/dispersants, anti-oxidants, combustion improvers, corrosion inhibitors, low temperature performance additives (improving the cloud point, sedimentation rate, filterability and/or low temperature flow), colorants, emulsion breakers, metal deactivators, anti-foaming agents, agents improving the cetane number, compatibilizing agents, lubricity additives, anti-wear agents and/or friction modifiers, and one or more solvents or co-solvents. The use of the additives according to the invention makes it possible to improve the lacquering resistance at the level of the fuel injectors, and thus limit the formation (the deposit) of soap and/or varnish in the presence of the additives such as the deposit reducers and/or detergent and/or dispersants. The use of these additives in (bio) gas oil vehicle fuels makes it possible to reduce the blockage rate and deterioration in the fuel admission or injection system, in particular on the injection pump.

The bio gas oil vehicle fuels (liquid fuels for compression engines) can comprise middle distillates having a boiling point comprised between 100 and 500° C.; their incipient crystallization temperature ICT is often above or equal to −20° C., in general comprised between −15° C. and +10° C. These distillates are mixtures of bases that can be selected for example from the distillates obtained by direct distillation of gasoline or crude hydrocarbons, vacuum distillates, hydrotreated distillates, distillates originating from the catalytic cracking and/or hydrocracking of vacuum distillates, the distillates resulting from ARDS (atmospheric residue desulphurization) type conversion processes and/or visbreaking. The (bio) gas oil vehicle fuels can also contain light cuts such as the gasolines originating from distillation, catalytic or thermal cracking units, alkylation, isomerization, desulphurization units and steam cracking units.

Moreover, the (bio) gas oil vehicle fuels can contain novel sources of distillates, among which there can be mentioned in particular:

heavier cuts originating from the cracking and visbreaking processes concentrated in heavy paraffins, comprising more than 18 carbon atoms,

synthetic distillates originating from gas conversion such as those originating from the Fischer Tropsch process,

synthetic distillates resulting from the treatment of biomass of vegetable and/or animal origin, such as in particular NexBTL, alone or in a mixture,

coker gas oils,

alcohols, such as methanol, ethanol, butanols, ethers, (MTBE, ETBE, etc) in general used in a mixture with the gasoline vehicle fuels, but sometimes with heavier vehicle fuels of the gas oil type,

vegetable and/or animal oils and/or their esters, such as vegetable oil or fatty acid methyl or ethyl esters (VOME, FAME, VOEE, FAEE),

hydrotreated and/or hydrocracked and/or hydrodeoxygenated (HDO) vegetable and/or animal oils,

These novel vehicle fuel and fuel bases can be used alone or in a mixture with conventional petroleum middle distillates as vehicle fuel base(s); they generally comprise paraffin long chains greater than or equal to 10 carbon atoms, preferably from C₁₄ to C₃₀. Within the framework of the present invention, the (bio) gas oil vehicle fuels have a sulphur content less than or equal to 500 ppm by mass, advantageously less than or equal to 100 ppm by mass, and capable of being reduced to a content less than or equal to 50 ppm by mass, or even less than or equal to 10 ppm by mass (this is the case of diesel fuels for current vehicles for which the sulphur content according to European standard EN 590 currently in force must be less than or equal to 10 ppm by mass).

The additives providing resistance to lacquering, i.e. to the formation of soap and/or varnish in the internal parts of the injection systems of engines for (bio) gas oil vehicle fuels according to the invention can be incorporated in the vehicle fuels up to a value of 10% by mass. Advantageously the concentration of partial esters according to the invention in the final vehicle fuel is comprised between 20 and 1000 ppm by mass and advantageously between 30 and 200 ppm by mass, i.e. ppm by mass relative to the total mass of the vehicle fuel with additives.

According to an embodiment, the higher-grade (bio) gas oil compositions contain at least 20 ppm by mass of at least one additive according to the invention and optionally at least one or more other functional additives. Preferably, the concentration of additives according to the invention in the composition, i.e. the concentration of partial ester can vary from 20 to 1000 ppm by mass, and more particularly from 30 to 200 ppm by mass m/m. Among the other functional additives, the lacquering resistance additives of the present invention can be used alone or in a mixture with deposit reducers and/or detergents and/or dispersants, anti-oxidants, combustion improvers, corrosion inhibitors, low temperature performance additives (improving the cloud point, sedimentation rate, filterability and/or low temperature flow), colorants, emulsion breakers, metal deactivators, anti-foaming agents, agents improving the cetane number, anti-wear and lubricity additives and/or friction modifiers, co-solvents, compatibilizing agents etc.

The other functional additive(s) can be chosen non-limitatively from:

-   -   combustion-improving additives; for vehicle fuels of the gas oil         type, there can be mentioned cetane booster additives, in         particular (but non-limitatively chosen from alkyl nitrates,         preferably 2-ethyl hexyl nitrate, aryl peroxides, preferably         benzyl peroxide, and alkyl peroxides, preferably di tert-butyl         peroxide; for vehicle fuels of the gasoline type, there can be         mentioned octane number improver additives; for fuel such as         domestic heating oil, heavy fuel oil, marine diesel oil, there         can be mentioned methyl cyclopentadienyl manganese tricarbonyl         (MMT);     -   anti-oxidant additives, such as aliphatic, aromatic amines,         hindered phenols, such as BHT, BHQ;     -   emulsion breakers or demulsifiers;     -   anti-static or conductivity improver additives;     -   colorants;     -   anti-foaming additives, in particular (but non-limitatively)         chosen for example from polysiloxanes, oxyalkylated         polysiloxanes, and fatty acid amides originating from vegetable         or animal oils; examples of such additives are given in EP 861         182, EP 663 000, EP 736 590;     -   the detergent or dispersant additives, in particular (but         non-limitatively) chosen from the group constituted by the         amines, succinimides, succinamides, alkenylsuccinimides,         polyalkylamines, polyalkyl polyamines, polyetheramines, Mannich         bases; examples of such additives are given in EP 938 535;     -   anti-corrosion additives such as ammonium salts of carboxylic         acids;     -   chelating agents and/or metal sequestering agents, such as         triazoles, disalicylidene alkylene diamines, and in particular         N,N′ bis(salicylidene)1,3-propane diamine;     -   low temperature performance additives and in particular         additives for improving the cloud point, in particular, (but         non-limitatively) chosen from the group constituted by the         long-chain olefin/(meth)acrylic ester/maleimide terpolymers, and         the polymers of fumaric/maleic acid esters. Examples of such         additives are given in EP 71 513, EP 100 248, FR 2 528 051, FR 2         528 423, EP1 12 195, EP 1 727 58, EP 271 385, EP 291367;         anti-sedimentation and/or dispersant additives for paraffins in         particular (but non-limitatively) chosen from the group         constituted by the (meth)acrylic acid/alkyl (meth)acrylate         copolymers amidified by a polyamine, alkenylsuccinimides derived         from polyamine, phthalamic acid and double-chain fatty acid         derivatives; alkyl phenol/aldehyde resins; examples of such         additives are given in EP 261 959, EP 593 331, EP 674 689, EP         327 423, EP 512 889, EP 832 172; U.S. Patent Publication No.         2005/0223631; U.S. Pat. No. 5,998,530; WO 93/14178;         multi-functional low temperature operability additives chosen in         particular from the group constituted by olefin- and alkenyl         nitrate-based polymers such as those described in EP 573 490;     -   other additives improving the low temperature performance and         the filterability (CFI), such as EVA and/or EVP copolymers;     -   metal passivators, such as triazoles, alkylated benzotriazoles;     -   acidity neutralizers such as cyclic alkylamines;     -   markers, in particular the markers mandated by regulations, for         example the colorants specific to each type of vehicle fuel or         fuel.     -   fragrancing agents or agents for masking odours, such as those         described in EP 1 591 514;     -   lubricity additives, anti-wear agents and/or friction modifiers         other than those described above, in particular (but         non-limitatively) chosen from the group constituted by fatty         acids and their ester or amide derivatives, in particular         glycerol monooleate, and derivatives of mono- and polycyclic         carboxylic acids; examples of such additives are given in the         following documents: EP 680 506, EP 860 494, WO 98/04656, EP 915         944, FR2 772 783, FR 2 772 784.

The optional other additives are generally incorporated in quantities varying from 50 to 1500 ppm m/m, i.e. ppm by mass relative to the total mass of the vehicle fuel with additives.

These additives can be incorporated into the fuels following any known method; by way of example, the additive or the mixture of additives can be incorporated in concentrate form comprising the additive(s) and a solvent, compatible with the (bio) diesel fuel, the additive being dispersed or dissolved in the solvent. Such concentrates in general contain from 20 to 95% by mass of solvents. A person skilled in the art will easily adapt the concentration of additives according to the invention as a function of any dilution of the additive in a solvent, the possible presence of other components originating for example from the esterification reaction and/or other functional additives incorporated in the final vehicle fuel. The solvents are organic solvents that generally contain hydrocarbon solvents. By way of example of solvents, there can be mentioned petroleum fractions, such as naphtha, kerosene, heating oil; aliphatic and/or aromatic hydrocarbons such as hexane, pentane, decane, pentadecane, toluene, xylene, and/or ethylbenzene and alkoxyalkanols such as 2-butoxyethanol and/or mixtures of hydrocarbons such as mixtures of commercial solvents such as for example Solvarex 10, Solvarex LN, Solvent Naphtha, Shellsol AB, Shellsol D, Solvesso 150, Solvesso 150 ND, Solvesso 200, Exxsol, ISOPAR and optionally co-solvents or combatibilizing agents, such as 2-ethylhexanol, decanol, isodecanol and/or isotridecanol.

The invention relates to the use of at least one additive composition according to the invention incorporated in a vehicle fuel of the higher-grade (bio) gas oil type for improving the resistance to lacquering, i.e. fouling on the head and/or on the body of the needles of the fuel injection system but also in the whole needle lift control system (valves) of the injection system, in particular for engines provided with high-pressure direct fuel injection systems, with which most vehicles complying with the Euro 3 and more recent regulations are equipped. According to a particular embodiment, the subject of the present invention also relates to the use of a composition of (bio) gas oil vehicle fuel as described above, in order to limit the soap and/or varnish deposits in the internal parts of the injection systems of the engines using said composition, preferably direct injection engines, in particular high-pressure direct injection engines.

The subject of the present invention also relates to a process for limiting the soap and/or varnish deposits in internal parts of the injection system of an engine for (bio) gas oil vehicle fuels (diesel engines) having a sulphur content less than or equal to 500 ppm by mass, said process comprising the combustion in said engine of a (bio) gas oil vehicle fuel composition as defined above. Preferably, the process applies to direct injection engines, in particular high-pressure direct injection engines. Thus, the process according to the invention avoids and prevents the formation of deposits of soap and/or varnish in the internal parts of the injection system of the engine, in order to keep said engine clean. Advantageously, the process according to the present invention removes the soap and/or varnish deposited in the internal parts of the injection system of the engine, for a curative action, cleaning up the engine.

EXAMPLES

In order to test the performances of these additives according to the invention, the inventors have also developed a novel method that is reliable and robust for evaluating the sensitivity of (bio) gas oil vehicle fuels, in particular those of higher grade, to lacquering. This method, unlike the methods described in the publications cited above, is not a laboratory method but is based on engine tests and is therefore of industrial interest and makes it possible to quantify the effectiveness of the additives or of the additive compositions against lacquering.

The method for measuring lacquering developed by the inventors is detailed below:

The engine used is a four-cylinder, 16-valve, high-pressure injection common rail diesel engine with a cylinder capacity of 1500 cm³ and a power of 80 hp: regulation of the fuel injection pressure takes place in the high-pressure part of the pump.

The power point is used over a period of 40 h at 4000 rpm; the position of the injector in the chamber has been lowered by 1 mm relative to its nominal position, which on the one hand promotes the release of thermal energy from combustion, and on the other hand brings the injector closer to the combustion chamber.

The flow rate of vehicle fuel injected is adjusted so as to obtain an exhaust temperature of 750° C. at the start of the test.

The injection advance was increased by 1.5° crankshaft relative to the nominal setting (changing from +12.5° to +14° crankshaft) still with the aim of increasing thermal stresses to which the injector nozzle is subjected.

Finally, to increase the stresses to which the vehicle fuel is subjected, the injection pressure was increased by 10 MPa relative to the nominal pressure (i.e. changing from 140 MPa to 150 MPa) and the temperature is set at 65° C. at the inlet of the high-pressure pump.

The technology used for the injectors requires a high fuel return, which promotes degradation of the vehicle fuel since it can be subjected to several cycles in the high-pressure pump and the high-pressure chamber before being injected into the combustion chamber.

A variant of the method for testing the clean-up effect (i.e. cleaning of type 1 and/or type 2 deposits) has also been developed. It is based on the preceding method but is separated into two 20 hour periods:

For the first 20 hours a higher-grade gas oil B7 is used (containing detergent of the PIBSI type and an acid product) known for its tendency to cause lacquering. After 20 hours, two of the four injectors are dismantled and assessed in order to verify the quantity of deposits present and then replaced by two new injectors.

For the last 20 hours of the test, the product to be assessed is used. At the end of the test (40 hours in total), the injectors are dismantled and assessed.

At the end of the test, three sets of two injectors are available:

Set 1: 2 injectors having undergone 20 hours of higher-grade vehicle fuel known for its tendency to cause lacquering.

Set 2: 2 injectors having undergone 20 hours of higher-grade vehicle fuel known for its tendency to cause lacquering+20 hours of product to be assessed.

Set 3: 2 injectors having undergone 20 hours of product to be assessed.

Expression of the Results:

In order to ensure the validity of the result, various parameters are monitored during the test: power, torque and fuel consumption indicate whether the injector is fouled or whether its operation has deteriorated through formation of deposits, since the operating point is the same throughout the test. The characteristic temperatures of the various fluids (cooling liquid, vehicle fuel, oil) allow the validity of the tests to be monitored. The vehicle fuel is adjusted to 65° C. at the pump inlet, and the cooling liquid is adjusted to 90° C. at the engine outlet.

The smoke values allow the combustion timing to be monitored at the start of the test (target value 3FSN) and ensure that it is properly repeatable from one test to the next. The injectors are dismantled at the end of the test in order to inspect and assess the deposits formed along the needles. The procedure adopted for assessing the needles is as follows:

The scale of scores varies from −2.5 (for a heavy deposit) to 10 (for a new needle without any deposit). The final score is a weighted average of the scores over all the assessed surfaces of the needle, i.e. the conical part and the body or cylindrical part of the needle.

Thus the cylindrical zone (directly following the conical part) represents 68% of the overall assessment of the needle and the conical zone represents 32% of the overall assessment of the needle. In order to facilitate the assessment, each of these two zones is divided into 4. In FIG. 4, the percentages shown correspond to one quarter of the surface area of the needles: the overall surface area weighting is therefore 17×4=68%. A product performance threshold was determined with respect to this assessment procedure: Result <4=Unsatisfactory, result >4=Satisfactory.

The following examples illustrate the invention without limiting it.

Example 1 Measurements of Lacquering Resistance

According to the procedure for measuring the lacquering resistance described above, the performance is assessed of several packets of additives introduced into a gas oil matrix representative of the French market (B7=gas oil produced in France containing 7% FAME (fatty acid methyl ester) and complying with EN 590). Details of each vehicle fuel composition tested, as well as the results obtained, are shown in Table 1.

The quantities shown in Table 1 are quantities by mass (m/m).

TABLE 1 Test No. A B C D E F Vehicle fuel B7 B7 B7 B7 B7 B7 PIBSI type diesel detergent — 330 170 170 170 330 ppm ppm ppm ppm ppm Fatty acid mixture, mainly — 200 — — — — oleic acid with an acid ppm number of 180 mg of KOH/g Sorbitan monooleate — — 200 — — 100 ppm ppm Pentaerythritol mono- + di- — — — 200 — — oleate ppm Type 1 deposits score 8.7 −1 7.2 4.1 7.2 5.2 Type 2 deposits score 7.1 −1 6.9 6.7 6.0 6.2 Overall score 8.2 −1 7.0 5.0 6.4 5.9

These tests clearly demonstrate the effectiveness of the products of the invention in preventing and limiting the formation of varnish or soap type deposits (keep-clean action), since the needle assessments results at the end of the tests are much better than the assessment result obtained when the vehicle fuel contains only a PIBSI capable of forming soaps on the injector needles.

Example 2 Measurements of Lacquering Resistance

According to the procedure for measuring the lacquering resistance in its clean-up version described above, the performance is assessed of several packets of additives introduced into a gas oil matrix representative of the French market (B7=gas oil produced in France containing 7% FAME (fatty acid methyl ester) and complying with EN 590). Details of each vehicle fuel composition tested, as well as the results obtained, are shown in Table 2. Note tests G, G′ and G″ correspond to the same test, with G corresponding to the result for the set of injectors 1, G′ corresponding to the result for the set of injectors 2 and G″ corresponding to the result for the set of injectors 3.

The quantities shown in Table 2 are quantities by mass (m/m)

TABLE 2 Test No. G G′ G″ Vehicle fuel B7 B7 B7 PIBSI type diesel detergent 330 ppm 330 then 170 ppm 170 ppm Fatty acid mixture, mainly oleic 200 ppm 200 then — acid with an acid number of 180 mg 0 ppm of KOH/g Sorbitan monooleate — 0 then 200 ppm 200 ppm Type 1 deposits score 2.6 3.7 6.2 Type 2 deposits score 1.4 3.7 6.5 Overall score 1.8 3.7 6.4

These tests demonstrate the curative effectiveness (clean-up action) of the products of the invention i.e. in removing the varnish or soap type deposits already formed on the needles since the assessment of the set of injectors G′ is better than that of the set of injectors G (significant cleaning of the needle has been started), and also confirms their preventive effectiveness (keep-clean action) since the assessment of the set of injectors G″ is much higher. 

1. Additives for limiting the soap and/or varnish deposits in internal parts of injection systems of engines for (bio) gas oil type vehicle fuels, having a sulphur content less than or equal to 500 ppm by mass, comprising at least 50% by mass of partial polyol ester(s), the polyol esters comprising x ester units, y hydroxylated units and z ether units, x, y and z being integers such that x varies from 1 to 10, y varies from 1 to 10, and z varies from 0 to
 6. 2. Additives according to claim 1, wherein the polyol esters are obtained by esterification of fatty acid(s) and linear and/or branched polyols optionally comprising (hetero)cycles of 5 to 6 atoms, bearing hydroxyl functions.
 3. Additives according to claim 1, wherein the polyol esters, the ester unit, hydroxylated unit and ether unit distribution is such that x varies from 1 to 4, y varies from 1 to 7 and z varies from 1 to
 3. 4. Additives according to claim 1, wherein the polyols R are chosen from the linear polyols comprising more than three hydroxyl functions and the polyols comprising at least one heterocycle of 5 or 6 atoms, optionally substituted by hydroxyl groups, these polyols being able to be used alone or in a mixture.
 5. Additives according to claim 1, wherein R is a polyol comprising at least four units presented in formula (I) below; H—(OCH₂)_(p)—(CHOH)_(q)—(CH₂OH)  (I) with p and q being integers, p being equal to or greater than 0, q is greater than 2, these numbers not being able to exceed
 10. 6. Additives according to claim 1, wherein R is a polyol comprising at least four units presented in general formula (II) below: H—(OCH₂)_(p)—(CR1R2)_(q)-(CH₂OH)  (II) with p and q being integers, p being equal to or greater than 0, q is greater than 1, these numbers not being able to exceed 5, R1 and R2 are identical or different and represent either the hydrogen atom, or a —CH3 or —C2H5 group, or a —CH2OH group.
 7. Additives according to claim 1, wherein R is a polyol comprising at least two heterocycles of 4 or 5 carbon atoms and an oxygen atom, connected by the formation of an acetal bond between a hydroxyl function of each ring, those heterocycles being optionally substituted by hydroxyl groups.
 8. Additives according to claim 1, wherein the partial polyol esters are chosen from the partial sorbitan esters, used alone or in a mixture.
 9. Additives according to claim 1, wherein the polyols R are chosen from the group comprising erythritol, xylitol, arabitol, ribitol, sorbitol, malitol, isomalitol, lactitol, sorbitan, volemitol, mannitol, pentaerythritol, 2-hydroxymethyl-1,3-propanediol, 1,1,1-tri(hydroxymethyl)ethane, trimethylolpropane and carbohydrates such as sucrose, fructose, maltose, glucose and saccharose.
 10. Additives according to claim 1, wherein the partial polyol esters are obtained by reaction of the polyols with at least one fatty acid with a chain length varying from 10 to 24 carbon atoms and/or at least one diacid substituted by at least one polymer, for example poly(iso)butene comprising from 8 to 100 carbon atoms.
 11. Additives according to claim 10, wherein the partial polyol esters are chosen from the group constituted by monoesters or diesters obtained from mono acids chosen from the stearic, isostearic, linolenic, oleic, linoleic, behenic, arachidonic, ricinoleic, palmitic, myristic, lauric, capric acids, and mixtures thereof and/or diacids chosen from the alkyl- or alkenylsuccinic, alkyl- or alkenylmaleic acids.
 12. A method for limiting the soap and/or varnish deposits in the internal parts of the injection systems of the engines for the (bio) gas oil vehicle fuels, having a sulphur content less than or equal to 500 ppm by mass the method comprising using the additive as defined in claim
 1. 13. The method according to claim 12, further comprising incorporating the additive in the (bio) gas oil vehicle fuels for the engines.
 14. The method according to claim 12, wherein the engines are direct injection engines.
 15. Compositions of (bio) gas oil vehicle fuel having a sulphur content less than or equal to 500 ppm by mass, comprising: at least one additive comprising at least 50% by mass of partial polyol ester(s), the polyol esters comprising x ester units, y hydroxylated units and z ether units, x, y and z being integers such that x varies from 1 to 10, y varies from 1 to 10, and z varies from 0 to 6; and optionally at least one or more other functional additives.
 16. The compositions of (bio) gas oil vehicle fuel according to claim 15, further comprising up to 10% by mass of one or more additional additives.
 17. The compositions according to claim 15, wherein the fuel is higher-grade (bio) gas oil vehicle fuel containing at least 50 ppm by mass of deposit reducers/detergents/dispersants, and containing at least 20 ppm by mass of the additive, and optionally at least one or more other functional additives.
 18. The compositions of (bio) gas oil vehicle fuel according to claim 15 having a mono- and di-ester concentration varying from 20 to 1000 ppm by mass m/m.
 19. (canceled)
 20. (canceled)
 21. A process comprising: limiting soap and/or varnish deposits in internal parts of an injection system of an engine for (bio) gas oil vehicle fuel (diesel engine) having a sulphur content less than or equal to 500 ppm by mass; and combustion in the engine of a composition comprising at least one additive comprising at least 50% by mass of partial polyol ester(s), the polyol esters comprising x ester units, y hydroxylated units and z ether units, x, y and z being integers such that x varies from 1 to 10, y varies from 1 to 10, and z varies from 0 to 6; and optionally at least one or more other functional additives.
 22. The process according to claim 21, wherein the engine is a direct injection engine.
 23. The process according to claim 21, further comprising preventing formation of the soap and/or varnish deposits in the internal parts of the injection system of the engine, in order to keep the engine clean.
 24. The process according to claim 21, further comprising removing the soap and/or varnish deposits in the internal parts of the injection system of the engine, for a curative action of cleaning up the engine. 